Sweep-memory voltage generator



April 11, 1961 W. H. WOODWORTH SWEEP-MEMORY VOLTAGE GENERATOR Filed Dec. 10, 1959 -o.c. VOLTAGE 39 37 E| OUTPUT W25 VOLTAGE 4 0 E0 7 o 31 o t 0.0. sxsum. E

0 27 FIG. I.

1.1-. FREQUENCY MIXER AMPLIFIER DISCRIMINATOR SWEEP- OSOlLLATOR MEMORY DEVICE u 47 FIG. 2.

INVENTOR.

WILLIAM H. WOODWORTH ing-and remember the value where stopped.

SWEEP-MEMORY VOLTAGE GENERATOR;

William H. Woodworth, China Lake, Califi, assignor to the United States of America as represented by the Secretary of the Navy Filed Dec. 10, 1959, Ser. No. 858,829 v 4 Claims.' (Cl. 2s0 -20) I i (Granted under Title 35, US. Code (1952), sec. 266) The invention herein described may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

' The present invention relates to alinear time-variant or sweep generator which may be stopped from'sweeping and remember the value where stopped. When stopped,

reduced to a minimum and a high order of memory is realized.

This device comprises a magnetic amplifier and RC circuitry which may be used as a sweep generator and/or as a memory device usedin conjunction with a radar tes Patent Patented Apr. 11, 1961 concentrically disposed and each is wound around and encloses both of coils 13 and 15. The magnetic amplifier'further includes a bridge network consisting of coil 13 and diode 25 in one leg, coil 15 and diode 27 in another leg and diodes 29 and 31 in each of the other two legs. An 'A.-.C; input E is connected across the bridge Y network between coils 13 and 15 and diodes 29 and 31,

it operates as an integrating amplifier wherein drift is which provides a light,.compact, inexpensive and-highly reliable unit. Y I

An object of the invention is to provide an inexpensive, light weight, compact and highly reliable linear. timevariant voltage sweep generator.

v Another object is to provide a linear.time-variant volt- 'agesweepgenerator whichlcanbe stopped from sweep- A further object isto provide a voltage memory device which operates as an integrating .amplifierwherein drift respectively. A magnetic amplifier of this type is conventional and the operation thereof is described in Magnetic Amplifiers, by Storm (published by John Wiley and Sons, 1955), pages 244-255. The D.-C. output of the magnetic amplifier is applied across output filter capacitor 33 and resistor 35 which are connected in parallel. The output voltage E is taken across resistor 35, the saw-tooth wave form being shown adjacent thereto. -A feedback including capacitor 37 is connected between one side of capacitor 33 and one end of coil 21 and the other side of coil 21 is connected to the other side of capacitor 33 and to ground. A negative D.-C. voltage E is series connected through resistor 39 to the junction between coil 21 and capacitor 37.

e The operation of the saw-tooth generator is as follows. Assuming the amplifier is operating initially at saturated core condition, the output voltage E thereof (always negative) is at maximum value, capacitor 37is charged as indicated and current I is flowing through resistor 39 in the direction shown. The gain of a magnetic amplifier of this type is extremely high and if there is an extremely small change in current flow in coil 21 there is a very large change of output voltage E and the voltage across capacitor 37 must therefore equal E If the amplifier '3 did nothave an extremely highgain, then if E,, varied from the voltage across capacitor 37 there would be finite current flow through coil 21, resulting in adrift or decrease of the voltage across capacitor 37 as well as E because of thelosses in coil'21. Therefore, byusing a capacitor feedback in conjunction with an extremely high gain'magnetic amplifier the-memory or holding of a predeterminedvoltage is excellent" thereby providing minimum drift, and linearity of the sweep is realized. if current flow I is drawn in the direction shown, due to the negative value of E; with relation to the positive charge. .011 capacitor 37, capacitor 37 will discharge through resistor 39 and there will be no current flow through coil 21 since the amplifier has high gain.- The current vflow through capacitor 37 is therefore equal to is reduced to a minimum and a high-order of memory is realized. 1 1

A still further object is toprovide a rriemorydevice in conjunction with a radar 'system'whereinthe oscillator frequency thereof is varied as a function of the memory 2 r V shown, ;.-wh1ch causes an increase in E of E is veryerapid snap action which results from the output voltage to provide a constant beat. frequency. 1

Other objects and many of theattendant advantages of Fig. 1 illustrates the circuitry" ofthe present invention which functions as asweep generator and/or a'memory the current flow through resistor 39 and this current flow is constant with respect to time. Therefore, the voltage across: capacitor 37 as well-as E will'decre'ase linearly with .respect to time. When E reaches its minimum value then current I will ,fiow in coil-21, in'the direction This 4 increase regenerative. action" due to the magnetic amplifier con flows through No. If the amplifier is shunted by resistor Fig. 2 illustrates the present invention as used in a radar system wherein the device shown in Fig. 1 functions both as a sweep generator and as a memory device; and .Fig; 3 is a graph showing the characteristics",of'a triag netic amplifier,.theabscissas denoting amper tu'rns and the ordin'ate deno'ting outputIvoltagef 9 Referring now .to Fig. l o'f'thedrawing sh R then r wheref -Ncis the number of-turns of coil-21; Np. is the 1 combined, number of turns of-coils 13 and-l5, R is the 21 The frequency of oscillation is I 7 -I p A R10; 0

resistance'ofyresistor 35 and Re is the resistance of coil snap action voltage increase of E continues until it reaches its maximum negative value which is primarily determined by the magnitude of E The charge on capacitor 37 follows the increase of E and upon reaching maximum value the current flow in coil 21 ceases. The operation then repeats resulting in saw-tooth oscillations. The natural frequency of the device increases as a function of the increase of the negative polarity of E since capacitor 37 discharges more rapidly, and the amplitude of E increases with increasing amplitude of E The system is prevented from oscillating by applying a D.-C. signal to terminals 40, 42 of coil 23 and, assuming coils 21 and 23 are wound in the same direction with the current flow in coil 23 in the direction shown. The value of this current flow determines the operating point of voltage E on the curve shown in Fig. 3 which voltage is maintained constant thereby providing a highly eifective memory action as previously explained.

' Referring now to Fig. 2 of the drawings, there is shown a radar system having a mixer stage 41 receiving the incoming and oscillator 47 signals, the output of which is applied to LP. amplifier 43, the output thereof being applied to frequency discriminator 45. The D.-C. output of frequency discriminator 45 is applied to coil 23 of the memory device 11 shown in Fig. 1. The frequency of oscillator 47, being of the reflex klystron type, for example, is determined by the value of E The memory device is used in this circuit to establish an oscillator frequency which maintains the beat frequency (sum or difference of the. oscillator frequency and the incoming signal frequency) at a constant value. Conventional values of this beat frequency f,, are between 30 and 70 megacycles. When the input frequency to frequency discriminator 45 is other than f then the output thereof will have either positive or negative polarity depending upon whether this input frequency is more or less, than f,,.

The operation of the device is as follows. Assume the input frequency to the discriminator is less than f and the D.-C. output of the discriminator is positive. positive D.-C. output is.applied to coil 23 of memory device 11 which. causes E to become greater. This greater E signal is'applied to the repeller of oscillator 47 which causes the output frequency thereof to increase thereby increasing the input frequency to the discriminator towards f and the discriminator output towards zero. The function is that of a closed loop servosystem wherein the, beat frequency is always maintained ata constant. value. independent of changes of the incoming signal. I

t The sweep, frequency range of oscillator 47 is deter-'- mined by the magnitude of the sweep of sweep-memory device 11. If no, signal is being received by the antenna or thefrequency of the antenna signal is outside of normal, limits to have mixer 41 deliver a beat frequency f acceptable by LF. amplifier 43 then sweep-memory device 11, will freely sweep. This is because the output of the LP. amplifier is zero and no current is flowing through comprising a magnetic amplifier having an input, output means including a diode bridge rectifier network and a control winding, a filter capacitor connected across said output means, a capacitor operatively interconnecting one side of said filter capacitor and one end of said control winding, the other end of said control winding operatively connected to the other side of said filter capacitor and to ground, negative potential means, a resistor interconnecting said negative potential means and said one end of said control winding and said capacitor whereby current linearily flows from said capacitor to said negative potential means until said capacitor is fully discharged at which time current then flows through said control winding to said negative potential means thereby providing a linear time-variant saw-tooth voltage across said output means.

2. The linear time-variant saw-tooth voltage generator in. accordance with claim 1 in which said magnetic am- This plifier has another control winding, a potential source operatively connected with said another control winding whereby current flow therethrough prevents current flow from said capacitor and maintains the output voltage at a constant value with respect to time.

3. The combination of a radar system including an incoming signal, a mixer, an LP. amplifier, a frequency discriminator, a sweep memory device and an oscillator, said incoming signal and the output signal of said oscillator operatively connected to said mixer, the output of said mixer having a beat frequency which is the sum or the difference of said incoming signal and said oscillator output signal, the output of said mixer being applied to the input of said I.F. amplifier, the output of said I.F. amplifier being applied to the input of said frequency discriminator, the output of said frequency discriminator being of given polarity when the beat signal is above a predetermined value and of opposite polarity when below said predetermined value, said sweep-memory device including a magnetic amplifier provided with powerand first and second control windings, an output and an input operatively connected to said power winding, capacitive feedback means from said output to said first control winding, and a potential source operatively 1 connected to said feedback means for drawing current therefrom, the output of said frequency discriminator connected. to said second control winding to vary the output of said magnetic amplifier as a function of .the output of said phase, discriminator, and the output of said magnetieamplifier connected to said oscillator to vary of LFramplifier output to said second control winding.

control winding 23 of the sweep-memory device. :The output of the LP. amplifier becomes finite onlyiwhen I the difference, between the oscillator and mixer frequencies iswithin the band pass of the LF. amplifier. Therefore, when the antenna receives a signal within the oscillator sweep frequency range the output of the LP. amplifier becomes finite and the system will lock upon it as previously explained. H 1

Obviously many modificatibns and variations of the present invention are possible infthe light of the above teachings. It is thereforejto {beunderstood thatwithin the scope of the appended claims the. invention-may 'be practiced otherwise than as specifically described.

What is claimed is:

1. A linear time-variant saw-tooth voltage generator v References Cited in the fileof this patent UNITED STATES PATENTS 2,764,719 Woodson Sept. 25, 1956 2,777,055, Goldberg Jan. 8, 1957 2,827,570 Lynn Mar. 18, 1958 2,838,671 Miller etal. June 10, 1958 2,848,674 Forman Aug. 19, 1958 2,852,669 Ashby Sept. 16, 1958 Bycer Ian. 13, 1959 

